Cleaning of subsea surfaces, such as the submersed parts of ship hulls, receives gradually more attention. One reason is the advantages of cleaning hulls of vessels in order to improve fuel economy due to reduced friction when sailing. Another reason is the resulting pollution, not only from released soft and hard marine or aquatic growth, but also possibly released or scraped-off anti-fouling agents, paint and other poisonous and harmful materials. Previously, the released material used to be left in the water at the site of cleaning, resulting in pollution and sediments that easily are swirled about by large ships. Patent publication U.S. Pat. No. 4,926,775 contains description and illustration of a tool useful for cleaning of subsea surfaces, but operation of the tool results in severe pollution.
However, in patent publication WO 2009/142506, two embodiments of a cup-shaped rotating tool with spraying nozzles and a central suction outlet are described, and related methods for cleaning. In one embodiment, the cup having integrated nozzles rotates, the rotation is due to the momentum from the cleaning fluid being sprayed out from the nozzles. In the other embodiment, rotary arms with nozzles rotate inside the cup, the rotation is about the central outlet, around which outlet the plumbing of a watery cleaning fluid supply is arranged. The tools have proved to work very well, but they are quite complicated and therefore rather expensive and susceptible to malfunction. Further, the rotating mass is large, the energy for rotation is taken from the flow energy of the cleaning fluid, resulting in less energy for cleaning. And even though the suction effect of the tools in operation is good, improved suction effect is desirable, which will facilitate the operation as the tool easier will follow the surface to be cleaned.
Accordingly, a demand exists for tools that are simpler, less expensive, even more reliable and with improved cleaning effect and suction effect. The objective of the present invention is to provide tools and methods that are beneficial with respect to the above mentioned demand.